1. Technical Field of the Invention
The present invention relates to a magnetic bearing control device for controlling a magnetic bearing that supports a rotor effecting high speed rotation such as TMP (Turbo Molecular Pump) in non-contact manner in a state of magnetic levitation.
2. Related Art
Generally, a magnetic bearing for supporting a rotor in non-contact manner is known as a bearing for the rotor effecting high speed rotation. A device using such magnetic bearing is a Turbo Molecular Pump (hereinafter referred to as “TMP”) used in the semiconductor manufacturing devices, for example. The Turbo Molecular Pump typically has a machine main body (pump main body) for supporting a rotation body (rotor) constituting a pump with a control type magnetic bearing in non-contact manner and rotating it with an electric motor, and a controller (magnetic bearing control device) for controlling the machine main body.
In recent years, the TMP magnetic bearing control device as described above has a main stream changed from the conventional analog control method to digital control method along with the advancements of digital technology. The related TMP magnetic bearing control device of the digital control method is disclosed in JP-A-11-210673, for example. This related TMP magnetic bearing control device includes a DSP (Digital Signal Processor) for controlling a magnetic bearing and an electric motor, a flash memory storing a processing program and the control parameters in the DSP, and a real time clock. In the related TMP magnetic bearing control device, the DSP memorizes the operation hysteresis and the malfunction occurrence hysteresis in the flash memory with the time based on the output of real time clock, thereby facilitating the failure or malfunction diagnosis.
By the way, the Turbo Molecular Pump comprises electrical or electronic parts with relatively short service life (duration of life). More specifically, the parts with relatively short duration of life may include a large capacity electrolytic capacitor contained in a cooling fan for cooling a rotor (pump) and a control device main body or a power source circuit. The duration of life of these parts, as well as the operation time of the maintenance operation recommended by the maker, are described in the document such as an instruction manual or a specification sheet. Therefore, the related TMP magnetic bearing control device allows the maintenance operation to be practiced at the user's risk.
However, actually, in the related TMP magnetic bearing control device, because there is no operation of collating or confirming the operation hysteresis memorized in the flash memory or the total operation time calculated from the time when the power source is turned ON to the time when it is turned OFF with respect to the duration of life described in the above document, or due to the document missing, or other reasons, the appropriate maintenance operation can not be surely effected on the user's side at all times, whereby there is the possibility that it would be employed until a malfunction or failure occurred. Therefore, when the related TMP magnetic bearing control device is employed, the maintenance operation can not be performed appropriately on the user's side, resulting in degraded performance or safety of the Turbo Molecular Pump.